476 
INDEX 
PAGE 
Oculars, care of. 15 
comparison. 24 
compensating. 15 
cross-haired. 55 
goniometer. 15 
Huygens. 12 
micrometer. 181 
negative. 12 
net ruled. 202 
par focal. 15 
positive. 12 
projection. 15 
Ramsden. 12 
Oil globules, optic behavior of. 229 
Optic axes of crystals. 254 
axial angles. 257 
Optics of compound microscope. i 
Ordinary ray. 52 
Orientating devices. 141 
Orthogonal illumination. 47 
Orthorhombic system, characteristics of. 268 
Oxalates, detection of. 427 
Paint films, examination of. ig6 
Paper fibers.456, 457 
Parallel extinction. 253 
Paraboloid dark-ground illumination. 36 
Penetrating power of objectives. 8 
Periodic system of Mendelejeff. 446 
Petrographic microscopes. 75 
Phosphates, detection of. 427 
Platinum cups. 296 
wires. 148 
Pleochroism. 263 
Polarizer. 53 
Polarization colors. 260 
tube. 166 
Polarized light. 50 
Polishing. 436 
Polymorphous crystals. 251 
Potassium, common salts. 327 
detection by chloroplatinic acid. 327 
perchloric acid. 330 
mercuric thiocyanate, preparation of. 450 
Prism vertical illuminators. 77 
Projected image scale in quantitative work. 206 
Pseudomorphs. 251 
